Book Image

Mastering QGIS - Second Edition

By : Kurt Menke, GISP, Paolo Corti, Richard Smith Jr., GISP, Luigi Pirelli, John Van Hoesen, GISP
Book Image

Mastering QGIS - Second Edition

By: Kurt Menke, GISP, Paolo Corti, Richard Smith Jr., GISP, Luigi Pirelli, John Van Hoesen, GISP

Overview of this book

QGIS is an open source solution to GIS. It is widely used by GIS professionals all over the world. It is the leading alternative to the proprietary GIS software. Although QGIS is described as intuitive, it is also by default complex. Knowing which tools to use and how to apply them is essential to producing valuable deliverables on time. Starting with a refresher on the QGIS basics, this book will take you all the way through to creating your first custom QGIS plugin. From the refresher, we will recap how to create, populate, and manage a spatial database. You’ll also walk through styling GIS data, from creating custom symbols and color ramps to using blending modes. In the next section, you will discover how to prepare vector, heat maps, and create live layer effects, labeling, and raster data for processing. You’ll also discover advanced data creation and editing techniques. The last third of the book covers the more technical aspects of QGIS such as using LAStools and GRASS GIS’s integration with the Processing Toolbox, how to automate workflows with batch processing, and how to create graphical models. Finally, you will see how to create and run Python data processing scripts and write your own QGIS plugin with pyqgis. By the end of the book, you will understand how to work with all the aspects of QGIS, and will be ready to use it for any type of GIS work.
Table of Contents (19 chapters)
Mastering QGIS - Second Edition
Credits
Foreword
About the Authors
About the Reviewer
www.PacktPub.com
Preface
Index

Repairing topological errors via topological editing


Once the geometry errors have been identified, the work of repairing the layer begins. In Chapter 1, A Refreshing Look at QGIS, we covered basic vector data editing that included layer-based snapping. In this final section, we will cover how to repair topological geometry errors via topological editing. We will continue to use the parcels.shp data as an example.

Note

Topological editing only works with polygon geometries.

The editing approach taken depends on the topological error you are addressing. In the last section, three types of error were found: gaps, overlaps, and duplicate geometries. These are three of the most common errors associated with polygon data and we will look at how to repair these three types of error.

Example 1 – resolving duplicate geometries

Duplicate geometries are the most straightforward errors to address. Here are the step by step directions for resolving this type of topological conflict:

  1. Toggle the editing option...